Asea Aktiebolag

Asea Ab

Asea Brown Boveri Ab

Gunnar Nimmersjo

Murari M Saha

A method and a device for determining the direction to a fault on a power transmission line in relation to a measuring station with the aid of phase currents and voltages, measured in the measuring station, by means of which change values .DELTA.U in the phase voltage, change values in the phase voltage .DELTA.UM of a line model and change values in the derivative .DELTA.I' of the phase current can be determined, and wherein for each measuring loop phase-ground the signal .DELTA.QL=(.DELTA.U-.DELTA.UM).multidot..DELTA.UI' is formed and if this value is smaller than a negative value assumed in advance, a fault lying ahead, in relation to the measuring station, has been detected, and wherein for each measuring loop phase-ground the signal .DELTA.QB =.DELTA.U.multidot..DELTA.UI' is formed and if this value is greater than a positive value assumed in advance, a fault lying behind, in relation to the measuring station, has been detected.

Method and device for determining the direction to a fault on a power

High resistance ground faults on a transmission line of an electrical power transmission network are detected with the aid of a device comprising a travelling wave model of the line located in measuring stations (P, Q) at either end of the line, which permits the voltage distribution along the line, seen both from P and from Q, to be obtained. A voltage .DELTA.U.sub.Qp is formed as the difference between a votlage in station P, calculated in the travelling wave model in Q, and the corresponding voltage one period earlier. A voltage .DELTA.U.sub.Pp is formed as the difference between a voltage calculated in the travelling wave model at P and the corresponding voltage one period earlier. The corresponding voltage differences .DELTA.U.sub.Pq and .DELTA.U.sub.Qq are calculated for station Q. The voltage difference .DELTA.P is then formed as the difference between .DELTA.U.sub.Qp and .DELTA.U.sub.Pp, and the corresponding .DELTA.Q is formed as the difference between .DELTA.U.sub.Pq and .DELTA.U.sub.Qq. Fault detection is obtained when .DELTA.P&gt;.epsilon..sub.p or when .DELTA.Q&gt;.epsilon..sub.q, where .crclbar..sub.p is the accepted voltage difference at P and .epsilon..sub.q is the corresponding value at Q.

Detection of high resistance faults in electrical power supply network

A method for location of a fault on a transmission line in a network for distribution and transmission of electric power uses a travelling wave model of the transmission line positioned in measuring stations (P, Q) at either end of the transmission line, to obtain the voltage distribution along the transmission line, seen from both station P and station Q. A voltage .DELTA.U.sub.Qp is generated as the difference between the voltage in station P, calculated in the travelling wave model in station Q, and the corresponding voltage one period/half period earlier. A voltage .DELTA.U.sub.Pp is generated as the difference between the voltage, calculated in the travelling wave model in station P, and the corresponding voltage one period/half period earlier. The corresponding voltage differences .DELTA.U.sub.Pp and .DELTA.U.sub.Qq are calculated for station Q. The voltage difference .DELTA.P is then generated as the difference between .DELTA.U.sub.Qp and .DELTA.U.sub.Pp and the corresponding voltage difference .DELTA.Q is generated as the difference between .DELTA.U.sub.Pq and .DELTA.U.sub.Qq. The fault distance PF is then obtained as PF=.DELTA.P.PQ/(.DELTA.P+.DELTA. Q), where PQ is the distance between the stations.

Fault location in a power supply network

A method and a device for directional detection of a fault on a power transmission line extending between two stations (P, Q). In one of the stations (P) there is a travelling wave model which, by means of currents and voltages measured in the station, calculates the voltage distirbution along the line. The direction to a fault is determined by monitoring changes in calculated voltages in the two stations. If a fault occurs between the stations, the voltage change occurring in a station (Q) between the voltage existing prior to a fault and after a fault can be estimated as .vertline..DELTA.Uq.vertline., and the corresponding voltage change occurring in the other station (P) can be estimated as .vertline..DELTA.Up.vertline., whereby according to the invention the difference .vertline..DELTA.Uq.vertline.-.vertline..DELTA.Up.vertline.&gt;0 signifies a fault on the line side of the station (P), i.e. a fault lying ahead of the measuring point. A fault lying behind station P is evidenced when .vertline..DELTA.Uq.vertline.-.vertline..DELTA.Up.vertline.&lt;0.

Directional detection in connection with faults in a power supply network

A method and device for range limitation and direct tripping for protection in the event of a fault on an electrical power line extending between two stations (P, Q) involves employing a travelling wave model in one of the stations (P) which, with the aid of measured currents and voltages in that station, to calculate the voltage distribution at a number of control points along the line. The range of the protection device is indicated as the distance between the measuring station and that control point for which a voltage difference (.delta.u) becomes equal to zero. The voltage difference consists of the difference between the absolute value of a voltage differene between the absolute value of a voltage difference (.DELTA.u), formed as the sum of a voltage value (U') calculated with the travelling wave model for the control point at a certain time, and the corresponding voltage value (U') one half-period earlier and the absolute value of the latter voltage value. When the voltage difference becomes greater than zero, direct tripping can be initiated.

Range limitation for a protection device in a power supply network

A method and a device for distance protection and location of a fault point on a transmission line based on voltage waves emitted from a measuring point towards a fault point and corresponding waves reflected from a fault point, which are included in a travelling wave model of a transmission line. At certain regular intervals, a measurement is effected of the instantaneous values of the current and the voltage at an end point of the transmission line, for example at a station. Based on these measured values, and with the aid of the travelling wave model, it is possible to calculate the voltage at a number of control points along the transmission line. If the line is energized and the calculated control voltages at two control points have different signs during a time longer than a time corresponding to normal phase difference between the two voltages, there is a fault on the line between these points. By interpolation, it is possible, based on the distance between the points in question and the calculated control voltages, to precisely locate the fault point in the case of a low resistance fault.

Detection and location of a fault point based on a travelling wave model

In an arrangement for level and sequence detection in a directional wave detector, which has a three-phase directional wave detector with two inputs per phase and three single phase and one three-phase tripping output and one three-phase blocking output, with a level detector with one partial detector for each of the single-phase tripping outputs and the three-phase blocking output, the level detector is provided with a further partial detector which is connected to the three-phase tripping output of the wave detector and the two partial detectors which are connected to the three-phase outputs of the wave detector have a lower reference level than the other partial detectors which are connected to the single-phase tripping outputs of the wave detector.

Growing community of inventors

Vaster.ang.s, Sweden

Gunnar Nimmersjo